LOS ANGELES -- You think all that musical magic you see on the Grammys just happens overnight?

No way, Jose. It takes months of planning, weeks of preparation and days of rehearsals by hundreds of musicians and crew members.

As part of our tireless (but incredibly tiring) effort to bring you every possible second of Grammy action between now and the big night on Sunday, we were able to find our way into a few of Friday's rehearsal sessions. Here's what we saw:

2 p.m. -- Green Day with the American Idiot cast

Security is crazy-tight at the Staples Center. Not only did we need to apply in advance for accreditation just to get in the door -- once we do get in, we have to empty our pockets and/or purses and go through a metal detector. We are given backstage pass-style stickers, told we must wear them at all times and escorted into the sectioned-off portion of the arena where the media (and a few lucky fans) are allowed to sit. Across the way, on the massive black stage, Bay Area pop-punk trio Green Day are running through 21 Guns (up for Best Rock Performance and Best Rock Song) with the cast of their new American Idiot musical and a string section. The song begins quietly with the young castmembers and the strings, then kicks into gear when a giant wall rises to reveal the band. The black-clad Billie Joe -- playing acoustic guitar -- swaps vocals with a female vocalist while the rest of the kids gather around, sing backup and pump their fists to the beat. Between all those vocalists and the dramatic arrangement, this version of the song sounds even more anthemic than the one on the CD -- if that's possible. After three run-throughs, each of which sounds about the same as the last, it's over.

A little more on that stage: It's very sleek, with two ramps that come forward from either side and meet in the middle at a set of lighted stairs. One would assume the little pits in the stage are for the orchestra. Above there are half a dozen video screens, masses of lights and plenty of neon. There's also a small circular satellite stage for introductions and whatnot in the centre of the arena.

4:30 p.m. -- Black Eyed Peas

The Peas know how to make an entrance -- their performance begins with them ascending from under the floor onto the stage. First up is Imma Be, which they perform while the lyrics pop up on the giant video screens behind them. I Gotta Feeling (vying for Record of the Year and Best Pop Performance) comes next, and includes a great video montage of fans who sent in YouTube videos of themselves performing the tune. It even includes a few VIP cameos by Timbaland, 50 Cent and Adam Lambert (that's one way to make sure he doesn't lose control on your awards show). Let's talk clothes: Fergie is wearing aviator shades, jeans, sky-high glittery black platforms and a white T-shirt that reads: "#1 Princess of the Posse." Fair enough. Will.i.am, meanwhile, is dressed in a grey jacket and nerdy round glasses. He seems in in good spirits -- he gives hugs to the technicians in the sound booth after rehearsal and spends a lot of time sending text messages on his BlackBerry. As for the other two guys ... ah, who cares?

5 p.m. -- Taylor Swift

The country-pop queen with has no shortage of fans of all ages -- even Canadian-born producer and arranger David Foster shows up to catch her rehearsal. Clad in a black mini-skirt and shaking her long blond curls, the eight-time nominee opens her segment with her new single Today Was a Fairytale, which sold a record-breaking 325,000 in its first week. As that song ends, Swift says: "And then my fairytale comes true -- Stevie Nicks joins me onstage." At which point -- such is the power of Taylor these days -- the Fleetwood Mac heroine obediently emerges to duet on two songs, including Swift's You Belong to Me. If all of Swift's wishes get granted so easily, expect her to take home a slew of hardware on Sunday. Meanwhile, expect us to try to sneak into some more rehearsals on Saturday -- including performances by Bon Jovi, Celine Dion, Lady Gaga and Elton John.